How often should you change an AC air filter?

Most manufacturers suggest every one to three months, sooner with pets, allergies or heavy use. Check your owner manual and inspect it monthly.

Which way does an AC filter go in?

The arrow printed on the filter frame points in the direction of airflow, toward the blower and away from the return grille.

What size air filter do I need?

The size is printed on the frame of the filter already in your system. Photograph it before you throw it out.

Did You Clean That? · No. 04

Your air conditioner is breathing through a dirty sock.

An air filter catches dust, dander and lint before it reaches your system. When it loads up, airflow drops, the system works harder, and the air in the house gets worse instead of better.

Maintain ItYour AC Air Filter

Print the one-page checklist

LaLa's 60-second version of this is coming.
Watch it here, or on TikTok, YouTube Shorts, Instagram or Pinterest.

The 30-second version

1.Your air conditioner is breathing through a dirty sock.
2.Turn the system off.
3.Find the filter.
4.Read the old filter before you toss it.
5.Note the airflow arrow.
6.If the system is still short cycling, freezing up or blowing warm after a fresh filter, that is a service call. A filter fixes airflow, not refrigerant or electrical problems.

Short on time? That's the whole thing. #DidYouCleanThat

Check

Filter size printed on the frame
Airflow arrow direction
Return vent or air handler slot
Date you last changed it

01 — The problem

Nobody changes the filter because nobody can remember where it is or what size it takes. Then the system runs longer, the bill goes up, and the vents blow dust around the house.

02 — Why you should care

A clogged filter restricts airflow and makes the system run longer for the same result.
Restricted airflow can freeze the coil and lead to a service call.
Dust and dander that get past a loaded filter end up in your ductwork.
It is one of the cheapest maintenance items in the entire house.

LaLa says

“This is a five dollar part and a two minute job. Write the date on the edge of the filter with a marker so future you does not have to guess.”

03 — What you need

The correct replacement filter, matched to the size printed on the old one
A marker to date the new filter
A vacuum for the vent grille
Your system's owner manual for the recommended filter type and schedule

04 — How to do it

01Turn the system off.Switch the thermostat to off so the blower is not pulling air while the slot is open.
02Find the filter.It sits either behind a large return air grille on a wall or ceiling, or in a slot at the air handler or furnace. Check your manual if you are not sure.
03Read the old filter before you toss it.The size is printed on the cardboard frame, something like 20x25x1. Take a photo of it.
04Note the airflow arrow.There is an arrow on the frame. It points toward the blower, away from the return. The new one goes in the same direction.
05Vacuum the grille and slot.A quick pass while it is open, so you are not pulling that dust straight into the new filter.
06Slide the new filter in and date it.Arrow the same way as the old one. Write the date on the frame with a marker, close the grille, turn the system back on.

Filter FinderQuestion 1 of 4

Do you know your filter size?

It's printed right on the cardboard frame of the filter already in your system.

05 — Don't do this

Don't force a filter that doesn't fit. Air will bypass the gap and the filter does nothing.
Don't install it backward. The arrow points toward the blower.
Don't wash a disposable filter. Washable filters are a different product and must be fully dry before reinstalling.
Don't jump to the highest-rated filter without checking your manual. Some systems are not designed for very restrictive filters.

06 — Know when to stop

If the system is still short cycling, freezing up or blowing warm after a fresh filter, that is a service call. A filter fixes airflow, not refrigerant or electrical problems.

07 — LaLa's pick

If LaLa says it works, it works. Nothing gets the seal until she's used it.

LaLa is testing this

Pleated filters in your exact size

Buy a few at once so the next change is not a trip to the store.

LaLa Approved

A permanent marker by the return vent

Dating the filter is the whole system for remembering.

Questions people actually ask

How often should you change an AC air filter?: Most manufacturers suggest every one to three months, sooner with pets, allergies or heavy use. Check your owner manual and inspect it monthly.
Which way does an AC filter go in?: The arrow printed on the filter frame points in the direction of airflow, toward the blower and away from the return grille.
What size air filter do I need?: The size is printed on the frame of the filter already in your system. Photograph it before you throw it out.

While we're at it

Dryer Vent

There's another lint trap you forgot about.

Refrigerator Coils

Your refrigerator may be working harder because of this.

08 — Ask LaLa™

Still stuck on this one?

Try something like “Where is my AC filter and what size do I need?” and tell her what's actually happening.